Suture needles with cutting edges are conventionally made with tip portions having at least two substantially flat surfaces with a cutting edge disposed between the at least two flat surfaces. The flat surfaces are at a slight angle with respect to the longitudinal axis of the needle; these surfaces converge to form the point of the needle. A common problem with needles of this type is burring or bending of the point of the needle because of insufficient metal at the point to resist the stresses imposed on the point during use.
Additionally, if four or more flat surfaces are used to form the tip portion of the needle, it is quite difficult to manufacture the needle to repeatedly achieve a point resulting from a common, perfect intersection of the four or more flat surfaces with the longitudinal centerline of the needle.
U.S. Pat. No. 3,094,123 to Kurtz attempts to address these problems by removing the point of a cutting needle by grinding it away into an arc-like shape with the arc substantially perpendicularly intersecting the longitudinal centerline of the needle. This solution strengthens the tip of the needle but compromises the piercing effectiveness of the needle.
U.S. Pat. No. 3,636,955, also to Kurtz, proposes an alternative solution by describing a point formed by grinding away the needle tip to form a single planar surface that the inventor calls a chisel-type cutting edge. The planar surface is preferably 45.degree. with respect to the longitudinal centerline of the needle. U.S. Pat. No. 4,128,351 also to Kurtz describes a similar solution. U.S. Pat. No. 4,513,747 to Smith proposes a similar solution wherein each flat surface of the tip portion is ground away at a greater angle with respect to the needle centerline than the angle formed by the remainder of the flat surface. This method thus requires an additional grinding step for each flat surface. If four flat surfaces are used, it does not avoid the manufacturing difficulty of achieving a common intersection point with the new tip surfaces.